Many imaging applications require systems to be able to detect stimulus pulses and recognize their pulse frequency. A pulse as a short duration stimulus with significantly higher signal strength than the image background. Some exemplary applications of pulse detection and pulse repetition frequency (PRF) decoding are laser range finding, laser see spot, and target designation and differentiation. Pulse detection capabilities can also be useful in a variety of commercial and industrial imaging systems.
The exemplary applications require an image sensor that can accurately isolate timing and image location of a pulse, when the pulse has a short duration. Typically, a timing accuracy of less than 50 microseconds is desired, although some applications can require a shorter detection time period. In each of the exemplary applications, a controller analyzes each pixel in a pixel array for pulse data after the full pixel array has provided imaging data to the controller. The process of providing data to the controller from a pixel is referred to as the pixel reading out to the controller. Analyzing an entire frame (full array) of pixels for pulse detection each time the array reads out introduces a pulse detection delay, limits a pulse detection speed to the frame rate of the pixel array, and increases the processing power required for the controller to perform the analysis.